Piston



July 23, 1929. N. A. CHRISTENSEN PISTON Filed July 15, 1926 INVENTOR M MMLM A TORNEY V Mann Patented July 23, 1929.

UNITED STATES NIELS A. CHRISTENSEN, OF CLEVELAND, OHIO.

PISTON.

Application filed July 15,

My invention relates to pistons and rel ates more particularly to pistons adaptable for use in fluid compressors, pumps, fluid operated. brakes, rams,- and the like, although my invention is not confined to such a use.

An object of my invention is to provide an improved form of piston wherein an eflicient seal maybe had between the walls of the cylinder, wherein the piston reciprocates, and the piston head, and in which the parts comprisin g the piston may be readily assembled.

Another object of my invention to provide a piston of the fluid pressure seal type wl'iereinlittle wear will occur between the sealing parts of the piston and the cylinder wall.

Another object of my invention is to provide a piston of this type which will not eli ect an undue amount of friction between the piston and the cylinder walls.

Another object of my invention is to provide a piston which can be readily, inexpensively manufactured and assembled and when assembled may be placed in a cyiinder of proper bore dimensions and will operate ellicientiy in connection with such cylinder.

Other objects of my invention and the invcntion itself will become apparent by reference to the following description of em- 'bodiments of my invention, illustrated in the accompanying drawings, forming a part of this specification.

Referring to the drawings Fig. 1 shows a longitudinal medial sectional view of an embodiment of my invention, certain iortions, however, being shown in elevation therein;

Fig. 2 shows a fragment of the piston of Fig. 1, the view being mostly in section; and

3 is a view of a fragment of a piston U .inder. mostly in longitudinal medial section, the view being of a modification of th emliiodimcnt illustrated in Fig. 1.

Referring first. to Figs. 1 and 2, at 1, I show the walls of a cylinder in which the piston of my invention is illustrated as having been placed for reciprocation therein; and at 2, I show the body of the piston having a centrally disposed opening 8 adapted to be inserted over the reduced end 5 of a tubular stem 4 and abut against a shoulder 6 formed thereon.

At 7, I show a relatively movable piston head of poppet valve form having a disk head portion beveled at 8 at its intraperipheral lower edge portion, an integral thickened 1926. Serial No. 122,597.

backing 18, and comprising also an integral tubular stem 9 depending axially from the disk head 7 and projected within the bore 10 of the tubular piston stein Nut 11 is threaded onto the reduced end 5 of the stem 4. A metallic cup 12 seated on the upper surface of the piston body is centrally perforatcd to admit the reduced end of the stem l, and is clamped by the nut 11 which is screwed against the top surface of the piston body 2, which adjoins the axial bore thereof. A compression spring l l, disposed in the bore 15, is compressed betwe n th shoulder 82 of the lower enlarged end of the stem 9 and the head of a bolt 20, the threaded end 16 being screw threaded into the axial threaded recess 33 of the stem 4. An expansion ring 17 is placed. within the side walls 10 of the cup 12, portions of the outer surfaces of which contact with the inner surfaces of cylinder walls 1, the ring 17 being substantially annular and preferably having a diagonal slit 23 at some point in length.

in inserting the ring 17 into the cup 19, the ring is contracted to bring the opposing surfaces along the slit more closely together against the resiliency of the ring material. When the ring is in place, it tends to expand and maintains, therefore, a pressure tending to expand the side walls 21. of the cup. This action is increased, moreover, by the cannning action exerted by the beveled surface 8 of the piston head 7 under the influence of the compressed spring 14-. In addition to the above two sources of pressure, which constantly tend to expand the cup side walls, this action is increased variably according to the variable amount of pressure exerted by the pressure of fluid contained in the cylinder chamber 22 and which exerts a pressure upon the entire upper surface of the piston head 7, and this pressure likewise is communicated by the camming action of the beveled surface 8 and the expansiblc ring 17 to the cup side walls.

Fluid pressure will be communicated, restrictedly, through the slit 23 of the ring 17 to the chamber 24 to the rear of the piston head. The slit 23 also provides a passage for the equalization of pressures in 24 and 22 upon a diminution of pressure in the cylinder chamber 22, whereupon in such. cases fluid under greater pressure will pass between the walls of the slit 19 to the cylinder chamber.

This will permit the parts to be more quickly restored to a position wherein the cup walls are not so tightly contacted with the cylinder side walls, during the pe'iod tollowing a period of high pressure in the cylinder chamber.

The volume ot the lluid containing space 2i, between the piston head and piston body is reduced by projecting portion such as 18 oi? the piston head, as illustrated in :Fig. 1, and as the annular ring 50 illustrated in Fig. th is less fluid under pressure is required to be used Lhan it the space were of larger volumetric content.

](\.'-t:;lll'0f-l cannot esci pc irom the chamber 2-1;. to the space to the rear of the pist' nor to atmosphere past the stem -l-. is. i

:ll; is provided between the shouldr' i, stein -l.- and the disloshaped head :5 so prevent leakage o l liuid under pressure.

it will be noted that I have provided a working contact element 'l'orminc' an integral head tor the tubular stem 4;, the retiactilc ellort ot the opeal'cd mechanism being exerted against each of the elements to retract the pistons after movement tbereot by l'luid pressure.

The ends oi? the cylinder are preferably closed by disks 27, each seated within an annular recess 4-?) concentric with the bored. boss 26 ot the disk central. portion. llhe rccess l is (to-axial with the inner walls of the cylinder, so that the piston may be prevented from cocking, which would ui'iduly increase the l'riction had With the side walls.

A hearing liner of relatively non-clrictional material is shown at 2 between the piston stem and the tubular surface 2%) of an openinc through the end wall 27 receiving the piston stem.

The cup side walls 31 are ot relatively thin metallic material an l continuous throughout their peripheral length, being sutiiriently resilient that when expanded by the ramming ellect oi the fluid pressed piston. read 7 acting through the ring 17 to make ight hitlll'lgl contact with the inner Walls oti he ryliruler l and the pressure being? thereil'ter relieved, the pressure of com? t had with the cylinder Walls will be reduced, thus reducing the resultanttrietion. The composite pislon, therefore, may be more readily restored to normal position, as illust 'ated, by the ret actile torce oi? the operated mechain acting; in the direction oi the arrows The ring 17 will d ribute the expanding pressure over a considerable port-ion of the cup side walls and by relieving the ring; 17 in portions thereof, particularly adjacent the bot loin wall 12 ot the cup, such pressure may be limited to a given peripheral portion of the. cup side walls, such the portion more nearly adjacent the rim of the cup, as illus trated. The angle of bevel 8 determines to a considerable extent whether the maximum pressure will l e evcrted more nearly towards the rim of the cup or relatively more remote there'lron'i.

in practice, the side walls oil the cup, which are forced into contact with the cylinder side walls in a manner above described, effect an lirient seal against the escape ot fluid under rure from the chamber 22; a relatively r'gje sealing; surface conflicting with the cyl side walls and the pressure per unitof at area is reduced, effecting a reduction in 'lrictional wear.

in Fl 3, have illustrated an embodiment. o my invention wherein an annular ring o iv preferably light impervious material such as aluminum, rubber, bakelite, or the like,

inserted within line space; Qel, being substituted for the portion l8 ot' the first described cinlnaliinent, and the head 51 in. this embodiment, being made. relatively thin. The re mainder ot the piston and associated parts are similar in construction to the piston 7 elf the embodiment of Fig. l. The annular is centrally apertured at and so dispom, d the space 53 between the piston head in 'l p g on body that the aperture rereives i l l Meme: tum in the piston head 51 is reduced ll'r' virtue ot decreasing the Weight of the thus described my inv mtio-n in spel odiments, I am aware that numerous :.tcn:-;ive de nirtures may be made from the embodin'ients herein illustrated and described but without dep: rt-in 't'rom the spirit oi? my invent-ion.

claim:

1. In a composite piston, the combination with a piston stem having an axial recess extending from an end and supporting a disk flange at such en d, an apertured cup seated on the disk flange and having a side wall disposied adjacent the 'all of a cylinder in which the piston is adapted to operate, a cumming element of approximately mushroom valve :lorm having; an axially recessed. stem, and a head flange, the end wall of the last named recess being apertured, the cannning element having an int 'a 'ieripheral beveled edge portion adapted to effect a. cainming expansion cfi'ort upon the side wall of the cup to press the same against the cylinder Walls, a bolt having a threaded end passed through the aperture in the said apertured end 'a ii and secured to the end wall of the recessed piston stem, and a compression spring interposed between the head of the bolt and the recessed end wall of the camining element stem, the outer surface of the eamming element head flange being exposed to fluid pressure within the cylinder, the effect of such fluid pressure and of the compression spring being aggre gated to effect expansion of the cup side Wall, and an annular ring interposed between the opposingfaces of the camming element and cup end Wall to reduce the fluid content of the :--;pace therebet-ween 2. in. a composite piston, the combination ill-3 ill) fit)

with a piston stem having an axial recess extending from an end and supporting a disk flange at such end, an apertured cup seated on the disk flange and having a side wall disposed adjacent the wall of a cylinder in which the piston is adapted to operate, a camming element of approz ziinately mushroom valve form having an axially recessed stem, and a head flange, the end wall of the last named recess being apertured, the camming element having an intraperipheral beveled edge portion adapted to effect a cumming expansion effort upon the side wallv of the cup to press the same against the cylinder wall, a bolt having a threaded end passed through the aperture in the said apertured end wall and secured to the end vall of the recessed piston stem, and a compression spring interposed between the head of the bolt and the recessed end wall of the camming elementstem, the outer surface of the camming element head flange being exposed to fluid. pressure 'ithin the cylinder, the effect of such fluid pressure and of the con'ipiession spring being 1ft gated to effect expansion of the cup side wall, and an annular ring interposed between the opposing faces of the cainming element and cup end wall to reduce the fluid content of the space therebetween, said piston stem and supported disk being removably secured together.

3. In a composite piston, the combination wi h a piston stem having an axial recess extending from an end and supporting a disk flange at such end, an apertured cup seated on the disk flange and having a side wall disposed adjacent the wall of a cylinder in which the piston is adapted to operate, a cammng element of approximately mushroom valve form having an axially recessed. stem, and a head flange, the end wall of the last named recess being apertured, the camming element having an intraperipheral beveled edge portion adapted to effect a cannning expansion effort upon the side wall of the cup to press the same against the cylinder wall, a bolt having a threaded end passed through the aperture in the said apertured end wall and secured to the end wall of the recessed piston stem, and a compression spring interposed between the head of the bolt and the recessed end wall of the cumming element stem, the outer surface of the cumming element head flange bein exposed to fluid pressure within the cylinder, the effect of such fluid pressure and of the compression spring being aggregated to effect expansion of the cup side wall, and an annular ring interposed between the opposing faces of the camming element and cup end wall to reduce the fluid content of the space therehetween, a ring interposed between the said beveled surface of the camming element and the cup side wall, and adapted to be expanded to communicate an expansive effort exerted by the element to the side wall of the cup.

In a composite piston, the combination with a piston stem having an axial recess extending from an end and supporting a dish flange at such end, an apertured cup seated on the disk flange and having a side wall disposed adjacent the wall of a cylinder in which the piston is adapted to operate, a camming element of approximately mushroom valve form having an axially recessed stem, and a head flange, the end wall of the last named recess being apertured, the camming element having an intra-peripheral beveled edge portion adapted to effect a camming expansion effort upon the side wall of the cup to press the same against the cylinder wall, a bolt having a threaded end passed through the aperture in the said apertured end wall and secured to the end wall of the recessed piston stern, and a compression spring interposed between the head of the bolt and the recessed end wall of the camming element stem, the outer surface of the camming element head flange being exposed to fluid pressure within the cylinder, the effect of such fluid pressure and of the compression spring being gated to effect expansion of the cup side wall, and an annular ring interposed between the opposing faces of the can'nning element and cup end wall to reduce the fluid content of the space therebetween, the piston stein adapted to communicate motion between the piston and a mechanism operating in connection therewith and responsive to a retractive effort of such mechanism, upon a release of fluid pressure in the cylinder above the piston, to restore the piston to normal. position, the material of the cup side wall being suficiently resilient to contract upon the relief of such fluid pressure and to thereby reduce the frictional pressure had between the cup side "all and the walls of the cylinder when outwardly cammed thereagainst.

In testimony whereof I hereunto afiix my signature this 16th day of June, 1926.

NIELS A. CHRISTENSEN. 

